Alaska Sen. Lisa Murkowski this week helped Senate Republicans block a bill that would require groups that pour hundreds of millions of dollars into influencing political campaigns to disclose who funds them.

Alaska Sen. Lisa Murkowski this week helped Senate Republicans block a bill that would require groups that pour hundreds of millions of dollars into influencing political campaigns to disclose who funds them.

The Republican Murkowski’s vote was unusual in that it followed an impassioned speech she made on the Senate floor declaring such shadow campaign funding “corrosive to democracy.”

“It’s done to influence the American political process in secret by contributing to organizations with very patriotic names. But they lurk behind post office boxes; there’s an anonymity I don’t think the American public expects or respects,” Murkowski said in her floor speech.

So why did she vote against the bill? Murkowski said in an interview that she felt the bill needed to be stronger, as well as bipartisan.

The bill, known as the DISCLOSE Act, would have forced unions, nonprofits and corporate interest groups that spend at least $10,000 in an election to file a report within 24 hours releasing the names of any donors who gave $10,000 or more.

Murkowski said the disclosure cutoff should be $5,000 instead of the $10,000 in the bill.

“Do I say yes to a bill I don’t believe is the right bill, just to make my point?” Murkowski told McClatchy. “I am working and I am committed to advancing a measure that is right and will work.”

Murkowski said she’s been talking with other senators and intends to introduce a campaign disclosure bill that she hopes will be bipartisan. “What I have to do is figure out how I can use my influence to get more Republicans on,” she said.

Senate Democrats forced the DISCLOSE Act vote at a time that airwaves across the nation are filled with election-year advertising, much of it attack ads, by political action committees and nonprofit groups funded by often anonymous donors.

“It’s only July and we’re already up to our elbows in dirty, distortive, negative attack ads. Imagine what it will be like by November,” said Alaska Democratic Sen. Mark Begich, who voted in favor of the bill.

The ads are “paid for by secret fat cats, unlimited deep pockets, money that no one knows where it comes from,” Begich said.

The vote on the DISCLOSE Act was on straight party lines, with all of the Senate Democrats voting in favor and all of the Republicans against. The measure received 53 Senate votes but needed 60 in order to overcome a Republican filibuster.

Senate Minority Leader Mitch McConnell, R-Ky., led the fight against the bill, saying it was a waste of time.

McConnell said it was a bill the Democrats knew wouldn’t pass and was just a chance for them “to make a fuss about a problem that doesn’t exist and blow a kiss to the unions for good measure.”

Murkowski said McConnell and her fellow Republican senators didn’t pressure her to vote against the DISCLOSE Act, and they didn’t know how she would vote. But she said the bill was clearly doomed to failure without Republican support, no matter how she personally voted, and that it’s going to take a bipartisan effort to have any hope of passing a bill.

The DISCLOSE act was sponsored by Sen. Sheldon Whitehouse, D-R.I.. His spokesman, Seth Larson, said the $10,000 cutoff was designed to protect groups like the National Rifle Association and the Sierra Club from having to disclose their membership lists, while still forcing disclosure of nearly all contributions to the giant political action committees known as “super PACS.”

“That said, Sen, Whitehouse remains open to hearing alternate proposals and looks forward to working with Sen. Murkowski and others to end secret money in elections,” Larson said.

The debate over what needs to be disclosed stems from the 2010 U.S. Supreme Court’s Citizens United ruling. That landmark ruling allowed unlimited political spending by corporations and labor unions so long as the spending is not coordinated with officials from the campaign the money is meant to help.

Murkowski’s historic write-in campaign for re-election benefited from Citizens United, which allowed massive spending on her behalf from Alaska’s Native corporations. But Murkowski has spoken out against the court ruling, and she did so again this week in the Senate.

“Alaskans have looked very critically at the Citizens United decision and its impact on campaigns in this country. I have made no secret of the fact that I disagree with the holdings of the Citizens United decision,” Murkowski said.